Let-back mechanism for looms

ABSTRACT

An improved let-back mechanism for looms having a manually operable actuating device for selectively controlling let-back of the fabric in increments of single picks.

United States Patent Lyman, Jr. et al.

[ June 24, 1975 LET-BACK MECHANISM FOR LOOMS Inventors: Merton C. Lyman, Jr., Woodstock,

Conn; Ronald Berry, Hopedale, Mass.

Rockwell International Corporation, Pittsburgh, Pa.

Filed: Mar. 8, 1974 Appl. No: 449,512

Assignee:

US. Cl. 139/313; 139/1 E Int. Cl D03d 49/00 Field of Search 139/313, 1 E

References Cited UNITED STATES PATENTS 12/1924 Norris 139/313 1,541,303 6/1925 Wilkinson 139/313 1,854,017 4/1932 Burdett 139/313' 2,664,115 12/1953 Gosnell 139/313 2,679,268 5/1954 Laferte 139/313 Primary Examiner-Louis K. Rimrodt Assistant E.\aminerSteven Hawkins 5 7 ABSTRACT An improved let-back mechanism for looms having a manually operable actuating device for selectively controlling let-back of the fabric in increments of single picks.

6 Claims, 3 Drawing Figures LET-BACK MECHANISM FOR LOOMS BACKGROUND OF THE INVENTION 1. Field of Invention The invention relates to looms wherein fabric as it is formed is incrementally advanced by a take-up roll which is rotated by the combination of a ratchet wheel carried on one end thereof and so-called feed and hold back pawls operatively associated with the ratchet wheel.

2. Description of the Prior Art In looms for weaving it is customary to provide a knockoff means which serves to initiate stopping of the looms. preferably by disconnecting the source of power and applying a brake to accelerate the stopping function. Such mechanism is normally dependent upon or functions in accordance with indications taken from a weft feeling or sensing mechanism, such as in and of itself well know to those conversant in this art.

Before restarting a loom after normal shutdown or after knockoff resulting from a weft break, it is common practice to let the fabric back by releasing the hold and feed pawls from the ratchet wheel so that the tension in the fabric reversely rotates said ratchet wheel and the take-up roll.

Let back of the fabric before restarting the loom after normal shutdown serves the purpose of preventing socalled start up marks in the fabric. When a loom has set idle even for a short period of time the tension to which the warp yarns and fabric are subjected will cause displacement of the fell line of said fabric. Under such condition, if the fabric is not let back, a thinned area will form in the fabric on the initial beat up by the looms reed by the packing of newly inserted picks of weft too tightly against the previously inserted pick.

Let back of the fabric before restarting the loom after knockoff resulting from a weft break permits the repositioning of the fell and fabric so that the broken pick can be removed and the loom restarted without forming a defect in said fabric.

In known fabric let-back mechanisms such as shown and described in US. Pat. No. 2,663,328 the distance the fabric is allowed to let back can be controlled for one or more picks and must be pre-set to the exact number of picks which it is desirable to let the fabric back.

The let-back mechanism for looms of the present invention is an improvement over known let-back mechanisms of the prior art. The instant invention provides a manually operable actuating means for selectively controlling let back of the fabric in increments of single picks. By simple repeated movement of the actuating means the fabric is let back the desired number of picks to correct a given condition prior to restarting the loom.

SUMMARY OF THE INVENTION The let-back mechanism according to the invention is provided with a pivotable lever in the form of a foot pedal having an upwardly directed control rod operatively associated with the pawl members which effect incremental rotation of the ratchet wheel and take-up roll. The control rod is selectively moveable, by depressing the foot pedal, from a rest position to first and second positions of operation. In the first position of operation, the control rod by means of a pivotal lug carried thereon is effective in disengaging the holdback pawl from the teeth of the rachet wheel. When the control rod reaches its second position of operation it is effective by means of an actuating collar fixed thereon in disengaging the feed pawl from the teeth of the ratchet wheel.

With both pawls disengaged from the teeth of the ratchet wheel the latter and the take-up roll will, under the tension in the fabric, commence to rotate reversely. This retrograde movement is limited to one tooth of the pick wheel which is the distance it is advanced for a single pick of weft. When the control rod is lowered to its second position of-operation and is in the process of disengaging the feed pawl, the holdback pawl loses contact with the pivotal lug and being spring biased is caused to pivot back into engagement with a tooth of the pick wheel. The return movement of the hold-back pawl is arranged and timed so as to engage a tooth of the ratchet wheel which is immediately adjacent to the tooth from which it was disengaged thereby limiting the reverse movement thereof one tooth of said pick wheel. By simply depressing the foot pedal again the mechanism will let back another tooth and can be repeated until the desired amount of let-back of the fabric has been obtained.

It is a general object of the invention to provide a manually operable fabric let-back mechanism for looms of simplified construction, having a minimum number of moving parts which are relatively inexpensive to manufacture and with long life expectancy.

A further and more specific object of the invention is to provide an improved let-back mechanism for looms which is manually operable and which can be actuated to selectively control let back of the fabric in increments of single picks.

These and other objects of the invention will become more fully apparent by reference to the appended claims and as the following detailed description proceeds in reference to the figures of drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view taken from the left hand side of a loom showing the mechanism according to the invention applied thereto,

FIG. 2 is a view similar to FIG. 1 showing the disengaging means in that position to effect disengagement of the feed pawl from the ratchet wheel and reengagement of the hold-back pawl therewith, and

FIG. 3 is a front view of the loom and mechanism shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing wherin only as much of a conventional loom structure is depicted as is necessary to a complete understanding of the invention, there is shown in FIG. 1 a portion of the left hand loomside 10. A bearing member 11 (FIGS. 2 and 3) is fixed to the forward upper portion of the loom by means of bolts 12 and rotatably supports a shaft 13 which extends outwardly beyond the loomside 10 in a direction normal thereto. In FIG. 3 a handwheel 14 is shown fixed on the outer end of shaft 13 and serves a purpose well known to those conversant in the weaving art. Immediately adjacent to the handwheel l4 shaft 13 supports a ratchet wheel 15 which is rotatable therewith. This ratchet wheel is advanced by a feed pawl 16 pivoted at 17 at the upper end of an actuating lever in the form of a two-armed lever 18 which is pivoted on the shaft 13 and which extends downwardly at arm 19 to have connected thereto at a pivot 20 one end of an adjustable link 21 (FIG. 1) by means of which the said pawland arm are oscillated to and fro. The opposite end of this adjustable link 21 is connected at a pivot 22'to the lower arm 23 of a double-armed lever generally indicated at 24, and the second arm 25 thereof has a second adjustable link 26 connected thereto at a pivot 27.

This link 26 is reciprocated by means of a crank mechanism 28, although any type of eccentric means may be employed and it is contemplated that said crank or eccentric be adjustable as to its eccentricity thereby to make longer or shorter the throw of links 26 and 21. This advantage can also be obtained by adjusting the pivot 20 at the forward end of the adjustable link 21 in a slot 29 provided in arm 19 of the two-armed lever 18 so that the effective length of that arm may be varied as desired. Additionally the length of both adjustable links 21 and 26 may be varied since the central portions thereof are internally threaded for the assembly of their end portions thereinto and therefor adjustable.

Referring to FIG. 1, a generally U-shaped plate memmber 30 assembles by means of bolts 31 to the forward upper side surface of the loomside 10. A slot 32 is provided in the plate member 30 adjacent its upper end and serves to adjustably and pivotally support a hold-back pawl 33 by means of a pin 34.

This hold-back pawl 33 is in the form ofa two-armed lever with one arm thereof extending in a generally forward direction which is identified by numeral 35 and provides the means for disengaging said pawl from engagement with the ratchet wheel and will be more fully described hereinafter.

A second two-armed lever is pivotally supported on the plate member 30 by means ofa pin 36 and includes a first rearwardly extending arcuated arm 37 (FIGS. 1 and 2) which is so disposed as to engage a pin 38 that extends from the sides of the feed pawl 16. This feed pawl is spring biased in the direction of the teeth of the ratchet wheel by means of a coil spring 39 having one end attached to the pin 38 and its opposite end to the upper arm of the two-armed lever 18 as at 40.

Hold-back pawl 33 is also spring biased in the direction of the teeth of the ratchet wheel 15 by means of a coil spring 41 having one end attached to said pawl as at 42 in FIG. 3 and its opposite end to a second forwardly extending arm 43 of the second two-armed lever as at 44.

The second forwardly extending arm 43 of the second two-armed lever is provided at its forward end with an integrally formed apertured guide 'member 45 through which the disengaging means according to the invention is caused to extend and which is in the form of a pawl control rod 46. Extending in a generally downwardly direction the pawl control rod 46 is caused to pass through a guide block 47 suitably mounted for swivel movement on a bracket 48 that is fixed to the plate member 30 by means of a bolt 49. The lower end of the pawl control rod 46 being threaded assembles in a bifuracated connector 50 which provides a means for increasing or decreasing the length of said rod.

A foot pedal 51 is pivotally attached to the lower forward side of the loomside 10 by means of a bolt 52 and is spring biased in an upwardly direction by means of a coil spring 53 one end of which is attached to the foot pedal as at 54 and the opposite end to a retainer 55 suitably attached to said loomside. The foot pedal 51 is of reduced thickness intermediate its ends as at 56 and the bifurcated end of the connector 50 is pivotally assembled thereto by means of a pin 57.

The upper end of the pawl control rod 46 is bifuracated and has a generally L-shaped lug member 58 pivotally assembled between the bifurcation thereof by means of a pin 59.

Below and adjacent to the lug member 58 the pawl control rod 46 has an actuating collar 60 fixed thereon by means of a set screw 61.

To summarize the operation, the ratchet wheel 15 is incrementally rotated by the feed pawl 16 which is oscillated to and fro by the two-armed lever 18 and its interconnecting linkage to the crank mechanism 28. The hold-back pawl 33 is arranged and functions in a well known manner to maintain each new position of the ratchet wheel as it is advanced by the feed pawl. This incremental rotation of the ratchet wheel is transmitted by shaft 13 through customary gearing 62 (FIG. 3) which is effective in rotating a take-up roll 63 for advancing fabric as it is formed.

Before starting the loom after normal shutdown or cessation due to absence of weft, the let-back mechanism is actuated by simply depressing the foot pedal 51.

As shown in FIG. 1 the foot pedal has been depressed a distance which places the pawl control rod 46 in its first position of operation whereat the L-shaped lug member has pivoted the let back pawl out of contact with the teeth of the ratchet wheel by means of its contact with arm 35 of the lever which pivotally supports said pawl.

FIG. 2 shows the foot pedal fully depressed which places the pawl control rod 46 in its second position of operation whereat the actuating collar 60 has pivoted arm 43 of the second two-armed lever downwardly so as to raise its arcuated arm 37 which through contact with pin 38 raises the feed pawl 16 out of contact with the teeth of the ratchet wheel 15.

With both the feed pawl and hold-back pawl disengaged from the teeth of the ratchet wheel, the tension to which the fabric is subjected will cause said ratchet wheel and the take-up roll to rotate reversely. This retrograde movement however is limited to one tooth of the ratchet wheel 15 for as shown in-FIG. 2, the pawl control rod 46 when moved to its second position of operation pulls the lug member 58 to a position below and out of contact with arm 35 of the double-armed lever which carries the hold-back pawl.

Release of the hold-back pawl is timed so that its biasing means will cause it to engage that tooth of the ratchet wheel immediately adjacent to the tooth from which it was disengaged.

If it is desirous to let back the fabric more than a single pick. an operator need only repeat actuation of the foot pedal for as many picks as is considered necessary for a given condition. Although the present invention has been described in connection with a preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and the appended claims.

We claim:

1. In combination with a loom having a take-up roll to advance fabric as it is formed with means for rotating the take-up roll including a ratchet. an actuating lever having a feed pawl engageable with the ratchet and a hold-back pawl for maintaining the positions of the roll advanced by the feed pawl, an improved means for selectively controlling let back of the fabric in increments of single picks comprising:

a. disengaging means mounted on the loom for movement between a rest position and first and second positions of operation;

i. said disengaging means including means for disengagement of the hold-back pawl at the first position of operation and for disengagement of the feed pawl at the second position of operation;

b. operating means linked to said disengaging means for moving the latter between its rest and operating positions; and

c. biasing means operatively connected to the holdback pawl for effecting its re-engagement with the ratchet after disengagement of the feed pawl therefrom.

2. The improved let back control according to claim 1 wherein said disengaging means includes a pawl control rod supported for sliding movement in a generally vertical direction.

3. The improved let back control according to claim 2 wherein said means for disengagement of the hold back pawl includes a lug member pivotally carried at one end of said pawl control rod.

4. The improved let back control according to claim 2 wherein said means for disengagement of the feed pawl includes an actuating collar fixed to said pawl control rod and a lever member operatively associated with said collar and the feed pawl.

5. The improved let back control according to claim 4 wherein said biasing means includes a coil spring having one end connected to the feed pawl and the other to the actuating lever.

6. The improved let back control according to claim 1 wherein said operating means includes a foot pedal pivotally attached to the loom and cooperating spring means for continually urging said disengaging means to its rest position. 

1. In combination with a loom having a take-up roll to advance fabric as it is formed with means for rotating the take-up roll including a ratchet, an actuating lever having a feed pawl engageable with the ratchet and a hold-back pawl for maintaining the positions of the roll advanced by the feed pawl, an improved means for selectively controlling let back of the fabric in increments of single picks comprising: a. disengaging means mounted on the loom for movement between a rest position and first and second positions of operation; i. said disengaging means including means for disengagement of the hold-back pawl at the first position of operation and for disengagement of the feed pawl at the second position of operation; b. operating means linked to said disengaging means for moving the latter between its rest and operating positions; and c. biasing means operatively connected to the hold-back pawl for effecting its re-engagement with the ratchet after disengagement of the feed pawl therefrom.
 2. The improved let back control according to claim 1 wherein said disengaging means includes a pawl control rod supported for sliding movement in a generally vertical direction.
 3. The improved let back control according to claim 2 wherein said means for disengagement of the hold back pawl includes a lug member pivotally carried at one end of said pawl control rod.
 4. The improved let back control according to claim 2 wherein said means for disengagement of the feed pawl includes an actuating collar fixed to said pawl control rod and a lever member operatively associated with said collar and the feed pawl.
 5. The improved let back control according to claim 4 wherein said biasing means includes a coil spring having one end connected to the feed pawl and the other to the actuating lever.
 6. The improved let back control according to claim 1 wherein said operating means includes a foot pedal pivotally attached to the loom and cooperating spring means for continually urging said dIsengaging means to its rest position. 